The Senate decided to send Senator Mike Duffy's audit report back to its internal committee for a second review, despite objections from the Liberal Senate leader, who argued the RCMP should be tasked with the job.

Senator James Cowan said he couldn't support referring Duffy's report to a Senate committee that he didn't trust could operate without "political interference." He moved that the matter should be sent to the police.

But the government countered that Duffy's report could be directed to the RCMP after it underwent a second look by the Senate's internal economy committee.

Government Senate Leader Marjory LeBreton is set to announce new travel rules for senators on Wednesday. They are expected to cover things such as documenting taxi claims, declaring the purpose of Senate travel and charging for travel by senators' companions.

She is expected to make a detailed speech in the Senate about the new rules at around 2 p.m. ET.

During Stephen Harper's speech to his caucus Tuesday, the prime minister said he was working closely with LeBreton to make changes to the Senate's rules and practices.

The debate on Tuesday evening was the first in the Senate since the audits on senators Duffy, Mac Harb and Patrick Brazeau were released, and the first since it was revealed Duffy's questionable expenses were repaid by a personal cheque from the prime minister's chief of staff.

Senators argued about exactly when the RCMP should be called in to investigate Duffy's expenses, though the RCMP has already indicated it is looking into the expense reports of all three senators who have been ordered to repay money.

Independent Senator Harb, who quit the Liberal caucus and is fighting an order to repay thousands of dollars for inappropriate claims, said in the Senate that "natural justice" demands that "rules cannot be changed and applied retroactively."

Harb raised a question of privilege, arguing his case be referred to the Senate rules committee.

Cowan raised a question of privilege as well, saying that the "secret gift" of a $90,000 cheque to Duffy from Nigel Wright, the prime minister's chief of staff, threatens the independence of the Senate. Cowan noted that media reports suggest promises were made to Duffy that the Senate would "go easy on him" if he used the cheque to repay his claims.

What followed was a question period unlike anything seen in the House of Commons.

Most of the questions were asked by Cowan and were directed to the government Senate leader, Marjory LeBreton. Cowan peppered her with queries about Wright's cheque and about whether she or the prime minister knew about it beforehand.

LeBreton, on her feet constantly to answer, replied: "Absolutely not. That is just ridiculous." She said the prime minister learned about the cheque from media reports, adding, "I know there are conspiracy theories running around the place."

Other Liberals also questioned LeBreton. She denied that she'd interfered with the Senate reports that used far gentler language in Duffy's case than appeared in Harb's or Brazeau's.

LeBreton said, "Obviously, the case of Senator Duffy is going back to internal committee," although she has not yet sought Senate approval to have Duffy's expenses audited further.

Senator Jim Munson, a former CTV journalist, asked LeBreton if she agreed there had been a coverup.

"I know you are a journalist," she replied, adding, "You run around promoting conspiracy theories."

Cowan spoke of the "odium, contempt and ridicule" with which Canadians now view the Senate. "I will not read into the record what Canadians think of the Senate," based on emails he said he has received and comments he's heard.

The Senate wants Harb and Brazeau to pay back $51,000 and $48,000, respectively, but both say they did nothing wrong.

Duffy said he would repay $90,000 before an audit of his expense claims was finished, but then did not fully co-operate with the process.

Senator Pamela Wallin's travel expenses, $321,000 since September 2010, are being reviewed, but that report by Deloitte isn't finished yet.

A Senate report has recommended that living and travel rules be tightened, proposing receipts should be required for all taxi trips, not just those over $30 as current rules dictate, and that senators should submit road travel logs when they claim mileage.

Harb says he checked the rules

Harb spoke at length about how unfairly he feels he's been treated. He said he had told a Senate clerk he'd moved to a home in the country and was renting an apartment in Ottawa, and would be claiming expenses for it. The clerk told him that would not be a problem, he said, adding, "The advice given to me cannot be ignored."

Harb, his voice rising as he spoke, asked if he should wear an ankle bracelet with a GPS to prove he was in what he calls his primary residence, a house near Pembroke more than 100 kilometres from Ottawa.

He angrily denied the findings of the Deloitte audit that he spent only 21 per cent of his time in his country home. But he seemed to mock the notion that 51 per cent would be the correct amount of time. "I'm sorry, it's not going to work that way. This is democracy, this is Canada," he said.

Harb's Liberal collegues did not defend him. Liberal Senator Joan Fraser said she did not find the rules about primary residence unclear, and said, in her opinion, Harb had no substantial case that his parliamentary privilege had been violated.

No one in the chamber echoed a suggestion from Conservative Senator Hugh Segal that the auditor general be invited to regularly examine senators' expenses.

The Senate Speaker, Noel Kinsella, said he would take the privilege questions raised by Harb and Cowan under advisement.

Duffy was not in the Senate chamber for the debate. Wallin, whose travel expenses are in the process of being audited, appeared for the first half hour and then left without making any comments.

Earlier Tuesday, Conservative Senator Jacques Demers commented on Duffy, Brazeau, Harb and Wallin, who have all left or been kicked out of their caucuses, saying, "If these people have done what has been speculated that they have done, they should be fired."

Hinting that he was considering leaving the Senate in disgust, Demers went on, speaking in English and French, "If it doesn't come out the way I want to ... personally, I'm not talking for other senators ... I'm gonna go."